Variable shorted coaxial line



April 27, 1965 VARIABLE SHORTED COAXIAL LINE sul' I: ll: l:

w. Ho'rlNE 3,181,094?"y Filed OC'C- 4. 1961 mmvrox William Hofzc Arma/KrUnited States Patent" M 3,181,094 VARIABLE SHORTED COAXIAL LINE WilliamHotine, Idyllwild, Calif., assigner to General Dynamics Corporation, SanDiego, Calif., a corporation of Delaware Filed ct. 4,*1961, Ser. No.142,820 '7 Claims. (Cl. S33-97) This invention relates to a variablyshorted coaxial line and more particularly to an arrangement forshorting the electrical circuit between the shield and inner conductorof a solid dielectric coaxial line at selected locations along the line.

In using high-frequency, electromagnetic wave energy, it is oftennecessary to employ tunable coaxial stub lines. Tunable stub lines inthe past have utilized air dielectric coaxial linesor strip lines.Disadvantages attendant with using such lines are that the lines oftenoccupy considerable space and are quite heavy. They also require acomplicated shorting arrangement that is expensive to make and maintain.

Therefore it is an object of this invention to provide an improvedvariably shorted coaxial line.

lt is another object of this invention to provide an improved,simplified, tunable coaxial stub line arrangement.

It is another object of this invention to provide an irnproved tunablecoaxial stub line arrangement having reduced space and weightrequirements.

It is another object of this invention to provide an improved device forvariably shorting solid dielectric coaxial lines. v

The variably-shorted, coaxial line of this invention includes a soliddielectric coaxial line with at least one inner conductor. The coaxialline has a narrow slot cut longitudinally along the line, through theouter shield and through the dielectric material exposing the innerconductor to contact from outside the shield. A variable shorting deviceencircles the shield and is capable of being slidably positioned alongthe shield and selectively retained in a given position along the lineby a spring arrangement. The spring arrangement includes spring contactmeans positioned on the metallic member and projecting through the slotin the line to connect the inner conductor electrically with the outershield anda spring means for resiliently holding the member at a givenposition along the coaxial line. The variable shorting device can bemoved along the longitudinal length of the coaxial member shorting theinner conductor to the outer shield at the position of the shortingdevice along the slot in the coaxial line and then locked in thatposition by a locking means. The particularly desired shorting locationof the shorting device may be adjusted through trial and error.

Other objects and many attendant advantages of this invention will bereadily apparent as the same becomes better understood by reference tothe following description when considered in connection with theaccompanying drawings in which like reference numerals designate likeparts throughout the iigures thereof and wherein:

FIGURE 1 `is Van illustrative view of the solid dielectric coaxial linewith the variable shorting device positioned thereon.

FlGURE 2 is a cross-sectional View of the variable shorting device ofthis invention.

llgd Patented Apr. 2?, 419665 FIGURE 3 is an end View of the variableshorting device of this invention.

FlGURE 4 is a partial cross-sectional view of a solid coaxial lineillustrating the slotted portion. Y

FIGURE 5 is a cross-sectional view of FIGURE 4 taken along line 5 5.

FIGURE 6 is a side view of a portion of a solid dielectric coaxial linewith the shorting device mounted thereon that forms a compact stub linearrangement.

Referring now to FGURE 1, a solid dielectric coaxial line l@ is shownhaving an outer shield 11 enclosing solid dielectric material 13 with aninner conductor 12 imbedded therein. For purposes of 'exempliiicatiomthe coaxial line 1d may comprise a solid dielectric 50 ohmV coaxial lineof the semi-rigid type having a steel copper plated inner conductor of.036 outside diameter and a copper, silver plated outer conductor orshield of .140 outer diameter with a solid Teflon lter of .116 outerdiameter. Such a semi-rigid coaxial line may be bent around a one-halfinch radius and Will remain set in its bent position.

The line 1t) is slotted radially outward from the inner conductor l2along the longitudinal length of the line 10 exposing the innerconductor. The length of the slotted portion of the line will be thatnecessary to afford the desired positioning of the variable shortingdevice. Slot 14 may be made with a saw or other known means andpreferably has a relatively narrow dimension with respect to the outercircumference of the line which narrow dimension slightly exceeds thewidth of spring contact means 22.

A variable shorting device comprises an outer metallic cylindricalmember 20 with shoulder or end ring portions 27. The inside diameter ofthe cylindrical member 20 and shoulder members 27 exceeds the outerdiameter of the coaxial line 10 permitting the shorting device to slidealong the length of line 10. Apertures 21 in shoulder .portions 27 arealigned to receive the hooked end portions of a metallic spring contactmeans 22. The hooked end portions extend through apertures 21 exiblyretaining the curved spring contact member 22 in the desired position.As can be seen spring contact member 22 is capable of projectingvthrough `slot 14 and making elec,-

.tric contact with inner conductor 12.

Vthe variable shorting device to desired location along line 10. A screwmeans 25 extends through a threaded opening in the Wall of cylindricalmember 20 for pressing against the spring means 24 thereby locking thevariable shorting device along the length of line 10.

In operation, high-frequency, electro-magnetic Wave energy flows throughinner conductor 12 in the normal manner. The variable shorting device 20is slid onto the end of line 10 in alignment with slot 14 so that thespring contact means 22 extends into slot 14 and bears on the innerconductor 12. The shorting device 20 is then slidably moved along thelength of the slotted portion of line 16 to the desired position. `Atthis desired position, spring contact means 22 electrically connectsconductor 12 to shield 11 either directly through cylindrical member 2)or through spring member 24 and then through cylindrical member 2t).After the desired position of the variable short is found by slidingadjustment, screw 2S is then turned locking the shortingdevice in thatposition. 'The end of screw 25 extending through the wall of cylindricalmember presses against the width dimension of leaf spring 24 therebyreducing the possibility of screw member 25 piercing the outer metallicshield 11 of the coaxial line 10.

As a representative showing in FIGURE 6, a 22 inch stub line made of thetype solid dielectric coaxial line previously described may be coiled tooccupy a one inch cube. Such a solid dielectric line would be equal inelectrical lengths to a 32 inch air dielectric line, as the electricallength is inversely proportional'to the square root of the dielectricconstant of the line insulating material. A 32 inch air dielectric linewould occupy considerably larger space than a one inchcube and could notbe bent to any coniguration as can the solid dielectric line.

Having described my invention, I claim:

l. A variably shorted coaxial line comprising, a substantially flexible,solid dielectric coaxial line with an outer metallic shield and at leastone inner conductor, said coaxial line having a longitudinal slotthrough said outer shield exposing said inner conductor along a givenlength of said line, a conductor member adapted to be slidablypositioned on said line along said slot and be in electrical contactwith said shield, contact means held by said conductor member andprojecting through said slot for Velectrically connecting said innerconductor to said conductor member at the particular point of locationof said conductor member along said length of said line, and resilientmeans held by said conductor member on the side of said linesubstantially opposite to said contact means for biasing said contactmeans into said contact with said inner conductor. Y

2. A variably shorted coaxial line comprising, a solid dielectriccoaxial line with an outer metallic shield and at vleast one innerconductor, said coaxial line having a narrow longitudinal slot throughsaid outer shield and through said solid dielectric exposing only oneside of said inner conductor along a given length of said line, acylindrical conductor member adapted to t around said line, saidconductor member having open ends and a diameter exceeding the diameterof said coaxial line, said open ends having inwardly projecting shoulderportions, said shoulder portions having aligned apertures therethroughat locations on opposite sides of said cylindrical member, springcontact means held by said apertures for electrically connecting saidinner conductor to said cylindrical member and spring means held by saidapertures for Vresiliently holding said cylindrical member at aparticular position along said line and for providing electrical contactbetween said shield and said cylindrical member.

V 3. A variably shortedy coaxial line comprising, a flexible soliddielectric coaxial line with Van outer metallic shield and an innerconductor, said coaxial line having a narrow longitudinal slot throughsaid outer shield and through said solid dielectric exposing said innerconductor along a given length of said line, a cylindrical conductormember adapted to fit around said line, said cylindrical member havingkopen ends and a diameter exceeding the diameter of said coaxial line,said open ends having inwardly projecting shoulder portions, saidshoulder portions having aligned apertures therethrough at locations onopposite sides of said cylindrical member, spring contact means forelectrically connecting said inner conductor to said cylindrical member,spring means for holding said cylindrical member to a particularposition lalong Vsaid line and for providing electrical contact betweensaid shield and said cylindrical member, said spring contact, meanshaving a curved length with hooked end portions, said hooked endportions projecting through aligned ones of said apertures in saidshoulders in a manner that said curved portion is biased away from saidcylindrical member and into said slot electrically contacting saidconductor, said spring means having va curved length. with hooked endportions, said hooked end portions projecting through other of saidaligned apertures ata position on the side opposite said spring contactmeans in a manner that said curved portion of said spring is biased awayfrom said cylindrical member and into electrical contact with saidshield, and screw means projecting through said cylindrical member andinto contact with said curved length of said spring means for forcingsaid curved length into contact with said shield locking said cylindri-Ycal member to said line at said particular position.

4. A variable shorting device VVfor a substantially exible, soliddielectric coaxial line having an outer metallic shield with alongitudinal slot through said outer shield and said solid dielectricexposing only one side of at least one inner conductor along a givenlength `of said line, saidshorting device comprising a conductor memberadapted to be slidably positioned on said line along said slot and inelectrical contact with `said shield, contact Vmeans held by saidconductor member and projecting through said slot for electricallycontacting only tsaid one side of said inner conductor ,connecting saidinner conductor to said conductor memberat the particular point oflocation of said conductor member along said length of said line, andresilient means heldfby said conductor Vmember on the side of said linesubstantially opposite to said contact means for biasing said contactmeans into said contact with said inner conductor.

5. In a variably shorted coaxial line having an outer metallic .shieldwith a longitudinal slot through said outer shield and through saidsolid dielectric exposing an inner conductor along a given length ofsaid line, a shorting device comprising a conductor member adapted tolit around said line and electrically contact said shield, spring Ycontact means held by said conductor member on oneside thereof andprojecting through said slot'for electrically connecting said conductorto said conductor member at a particular point of location of saidconductor member aiongsaid length of said slot, and spring means held bysaid conductor member on the side of said conductor member opposite saidone side for biasing said spring contact means into contact with saidinner conductor member.

6. A variable shorting device for a solid dielectric coaxial line havingan outer metallic shield with a longitudinal narrow slot through saidouter shield and through said solid dielectric exposing an innerconductor along a given length of said line, said shorting devicecomprising, a conductor member being capable of tting around said lineland in electrical contact with said shield, said conductor memberhaving a length shorter than the longitudinal length of said slot andbeing capable of slidably moving along said line, spring contact meansheld by said conductor'member on one side thereof and projecting throughsaid slot for electrically connecting said inner conductor to saidconductor member at a particular point of location of said conductormember along said length of said slot, spring means held by saidconductor member on the side of said conductor member opposite said oneside for biasing said spring contact means into contact with saidinnerconductor, and lock means coacting with lsaid spring means forlocking said conductor member at a location along said line.

7. A variable shorting device for -a solid dielectric coaxial linehaving an outer metallic shield with a longitudinal slot through saidouter shield and through said` solid dielectric exposing an innerconductor along a given length of said line, said shorting devicecomprising, a conductonmember adapted to tit around said line andelectrically Contact said shield, spring contact means held by saidconductor member on one side thereof and projecting through said slotfor electrically connecting said 3,181,094 5 6 inner conductor to saidconductor member at a particular Re'ereces Ced by ille Examiner point oflocation of said conductor member along said UNITED STATES PATENTSlength of said slot, spring means held by said conductor member on theside of said conductor member opposite 2,844,800 Z/SS EHS et al 333-82 XSaid one side for biasing said spn'ng contact means into 2,918,636 14/59 Snaplro 33E-97X centact with said inner conductor, and lock means co-3,125,199 3/64 Thompson 333-97 acting with said conductor member andsaid line for h a locking said conductor member to said line. HERMANKARL SAALBACH Plmay Examlle-

1. A VARIABLE SHORTED COAXIAL LINE COMPRISING, A SUBSTANTIALLY FLEXIBLE,SOLID DIELECTRIC COAXIAL LINE WITH AN OUTER METALLIC SHIELD AND AT LEASTONE INNER CONDUCTOR, SAID COAXIAL LINE HAVING A LONGITUDINAL SLOTTHROUGH SAID OUTER SHIELD EXPOSING SAID INNER CONDUCTOR ALONG A GIVENLENGTH OF SAID LINE, A CONDUCTOR MEMEBR ADAPTED TO BE SLIDABLYPOSITIONED ON SAID LINE ALONG SAID SLOT AND BE IN ELECTRICAL CONTACTWITH SAID SHIELD, CONTACT MEANS HELD BY SAID CONDUCTOR MEMBER ANDPROJECTING THROUGH SAID SLOT FOR ELECTRICALLY CONNECTING SAID INNERCONDUCTOR TO SAID CONDUCTOR